The experiments proposed here focus on testing our hypothesis that HIV-1 Tat and Vpr may stimulate dNTP biosynthesis by hijacking cellular pathways for efficient HIV-1 replication in terminally-differentiated host cells (macrophage and microglia). HIV-1 Tat may promote dNTP biosynthesis through the activation of survival and proliferation pathways, promoting entry into S phase and thus activation of genes associated with dNTP biosynthesis. Vpr, however, triggers the activation of the DNA damage pathway, which likely also enhances dNTP, enhancing DNA gap repair. Studies providing insight into Vpr's effect will examine the potential effect of different sources of Vpr, notably (i) cell-free (non-virion) Vpr, (ii) virion-associated Vpr and (iii) newly synthesized Vpr on the DNA gap-repair step that is essential for proviral DNA integration. Experiments addressing the mechanism of dNTP biosynthesis by expression of HIV-1 Tat will provide insight into the long-term survival of viral reservoirs such as macrophage and may explain their susceptibility to superinfection, thus increasing viral diversity. If specific cellular components involved in the effects elicited by Vpr or Tat (e.g. Akt, CHK1) are identified, then these studies may suggest possible new antiviral targets. [unreadable] [unreadable] [unreadable]